The field of the disclosure relates generally to rotary machines, and more particularly, to blades and damper sleeves for a rotor assembly.
At least some known rotary machines include at least one rotor assembly coupled to a rotor shaft. The rotor assembly includes a plurality of circumferentially-spaced blades that extend radially outward to define a stage of the rotary machine. For example, but not by way of limitation, the rotor assembly is part of a steam turbine, or part of a compressor or turbine section of a gas turbine engine. Each blade includes an airfoil that extends radially outward towards a casing of the rotary machine.
At least some known blade airfoils, such as but not limited to latter stage blade airfoils, are 40 inches or greater in length. At high rotational speeds, such as but not limited to 3000 rpm for airfoils greater than 48 inches in length or 3600 rpm for airfoils greater than 40 inches in length, at least some such blades are particularly susceptible to non-synchronous vibration that can be associated with flutter, rotating stall, or buffeting during operation of the rotary machine. An operational life cycle of at least some such blades is limited at least in part by fatigue resulting from non-synchronous vibratory stresses during rotary machine operation.
Vibration in at least some known blades of such size has been addressed through use of a rigid coupling between each blade and an adjacent blade, such as coupling the blades of a stage together through mid-span shrouds (or wings). For example, FIG. 1 is a perspective view of a prior art blade 18 with an airfoil having solid wing-style mid-span connectors 20. Mid-span connectors 20 are configured to couple directly against mid-span connectors 20 of adjacent blades to reduce vibrations during operation. However, such methods have been directed to improving blade coupling rather than to improving mechanical damping, and in at least some cases are inadequate to mitigate non-synchronous vibrations in blades having longer airfoils.